Question

Barisan geometri diketahui U1-U2+U3 = 9 dan U1xU2xU3 = 216 maka nilai dari U1 adalah.,.??

Answer 1

U1=12
u2=6
u3=3
12-6+3=9
12*6*3=216
jadi u1=12

Answer 2

(a/r) (a) (ar) = 216
a³ = 216
a = 6

a/r - a + ar = 9
6/r - 6 + 6r = 9
6 - 6r + 6r² = 9r
6r² - 15r + 6 = 0
(6r-3)(r-2) = 0

6r-3 = 0
r₁ = 3/6 = 1/2
r-2 = 0
r₂ = 2

r = 2
U₁ = a/r = 6/2 = 3